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<br />V. A. Sperling, Esq. <br />June 1, 2007 <br />Page 3 <br /> <br />As shown on the enclosed plots, there are periods during each representative <br />year when the Baseiine streamflow is much higher or lower than the actual streamflow <br />recorded at the gage. These o~servations are not consistent with the small differences <br />between the average monthly flows for the Baseline and historic conditions (simulated <br />on a monthly basis). which are shown on the enclosed Figure 6.5 from the user's <br />manual. Furthermo~e, the large differences observed during 2002 through 2003 are <br />particularly unexpected because there should be litt!e to no "backcasting" adjustment for <br />the current levels of use during these years. <br /> <br />As documented in our report. City of Durango Boating Park Hydrology Study, <br />Case No. 06CW09 (revised September 2006), the historic Animas River streamflow has <br />not shown an overall trend to increase or decrease since 1928. The large differences in <br />daily flows shown on the endosed p10ts are also incons:stent with this observation. <br /> <br />Comparison with ALP Requirements - We have compared the daily Baseline <br />stream~ow from the model with the ALP bypass requirements and pumping rates. This <br />comparison conside~s the simulated flows at the Durango gage and does not include <br />streamflow contributions from Lightner Creek. <br /> <br />The enclosed Table 2 indicates the number of days the ALP could divert its <br />maximum pumping rate of 280 cfs from the Animas River. We ceveloped this table by <br />su!:>tracting 280 cfs and the bypass flow amount from the daily values of Baseline <br />streamflow from the eWCB mcdei. As shown on this table, streamflow is available to ) <br />support the rraximum pumping rate 38 percent of the days during 1975 through 2003. \ <br />This information confirms the ALP will make the Animas River over-appropriated an0 <br />water critical, even when the eWeB's modeled flows are used. <br />